Each of User Equipments (UEs) UE1 and UE2, which have been attached to (or have subscribed to) a wireless communication network, may be assigned an IP address by the wireless communication network. The IP address may be assigned by a Packet Data Network (PDN) Gateway (P-GW), an IP server or some other network nodes in the wireless communication network. These IP addresses are local IP addresses in the wireless communication network.
FIG. 1 illustrates communication paths between UEs according to the related art.
Referring to FIG. 1, a UE1 100 and a UE2 102 may communicate with each other via the wireless communication network. In the wireless communication network, as for IP packets between the UE1 100 and the UE2 102, there may be a path 120 in which the IP packets may traverse via various network nodes. Examples of the network nodes may include evolved Node B (eNB) 112, eNB 122, Serving Gateway (S-GW) 114, S-GW 124, P-GW 116, and P-GW 126, a Packet Data Network (PDN) 110, and the like.
In communication between the UE1 100 and the UE2 102 via the wireless communication network, the UE1 100 and the UE2 102 may establish IP connections to some servers of the PDN 110. In the PDN 110, IP packets may be transmitted from the UE1 100 to the server of the PDN 110, and the server may transmit the IP packets to the UE2 102. Similarly, IP packets may be transmitted from the UE2 102 to the server of the PDN 110, and the server may transmit the IP packets to the UE1 100.
Packet bearers may be established between the UE1 100 and UE2 102 and the P-GW 116 and P-GW 126 to deliver IP packets from the UE1 100 and UE2 102 to the PDN 110. Typically, if a UE attaches with the wireless communication network, a default Evolved Packet System (EPS) bearer may be established between the UE and the P-GW. An EPS bearer between the UE1 100 and the P-GW 116 is a logical bearer, and may constitute a radio bearer between the UE1 100 and the eNB 112, an S1 bearer between the eNB 112 and the S-GW 114, and an S5 bearer between the S-GW 114 and the P-GW 116. When needed to provide differential Quality of Service (QoS) treatments to various IP flows of a UE, additional EPS bearers may be established between the UE and the P-GW of the PDN. The EPS bearer may be unidirectional or bidirectional. EPS bearers may also be established between the UE and P-GWs of multiple PDNs (e.g., Internet PDN, IP Multimedia Subsystem (IMS) PDN, and the like).
In the wireless communication network, if the P-GW 116 receives an Uplink (UL) IP packet on the EPS bearer, the P-GW 116 may convert a source IP address of the UE1 100 into a public IP address of a UE, and transmit the modified IP packet to the PDN 110. The P-GW 116 may have a mapping table (e.g., a packet filter table) between local IP addresses and public IP addresses for conversion of a source IP address in the UL direction.
The P-GW 116 may be designed to transmit UL IP packets received on the EPS bearer to the PDN 110. A destination IP address included in the UL IP packets received on the EPS bearer may not be modified by the P-GW 116. It is expected that because the UE1 100 is a source of the IP packet, the UE1 100 may have a public address of the destination and the public address of the destination may be filled in the IP packet.
In a Downlink (DL) direction, the P-GW 116 may receive IP packets from the PDN 110. The received IP packets may be mapped to appropriate EPS bearers in the DL direction based on DL traffic filters. The DL traffic filters may include a source IP address, a destination IP address, a source port number, destination IP addresses, a protocol type, and the like.
Alternatively, the UE1 100 and the UE2 102 may communicate with each other over a direct communication path 130. The direct communication path 130 between the UE1 100 and the UE2 102 may be established if the UE1 100 and the UE2 102 are in proximity to each other. The direct communication may be performed by a communication technique, for example, Wireless Fidelity (WiFi), Bluetooth, Zigbee, and/or the like. For direct communication, the UE1 100 and the UE2 102 may use the IP addresses, which have been assigned to the UE1 100 and the UE2 102 by the network (e.g., P-GWs 116 and 126, or IP server).
FIGS. 2A and 2B illustrate an IP packet structure and a protocol stack for direct communication between UEs according to the related art.
Referring to FIG. 2A, during the direction communication, an application layer 212 of the UE1 100 and an application layer 222 of the UE2 102 may interact with each other. Similarly, transport layer 214 of the UE1 100 and transport layer 224 of the UE2 102, IP layer 216 of the UE1 100, IP layer 226 of the UE2 102, wireless/wireline protocol stack layer 218 of the UE1 100, and wireless/wireline protocol stack layer 228 the UE2 102 may interact with each other. An example of the wireless protocol stack layer may include 3GPP-based wireless protocols, a WiFi protocol, and/or the like.
As illustrated in FIG. 2B, the UE1 100 and the UE2 102 may exchange IP addresses of each other, and transmit IP packet 200 and IP packet 202 carrying the IP addresses of each other. The IP packet 200 heading from the UE1 100 to the UE2 102 may have an IP address IP1 of the UE1 100 as a source IP address, and an IP address IP2 of the UE2 102 as a destination IP address. The IP packet 202 heading from the UE2 102 to the UE1 100 may have an IP address IP2 of the UE2 102 as a source IP address, and an IP address IP1 of the UE1 100 as a destination IP address.
Due to the change in channel conditions and the mobility of UEs, direct communication between the UEs is not feasible. If the direct communication path becomes weak and communication using the direct communication path is no longer feasible, the UE1 100 and the UE2 102 may be switched to a communication path via the wireless communication network. During the direct communication, the UE1 100 and the UE2 102 may transmit, to each other, IP packets carrying local IP addresses assigned by the wireless communication network. After the communication path is switched to the communication path via the wireless communication network, the UE1 100 and the UE2 102 may continue to transmit, to each other, IP packets carrying the local IP addresses assigned by the network. For example, the UE1 100 may continue to transmit an IP packet to the UE2 102. In this case, the IP packet may include a source IP address which is an IP address of the UE1 100, and a destination IP address which is an IP address of the UE2 102. These IP addresses are local IP address assigned by the network.
FIG. 3 illustrates a P-GW operation after communication path switching according to the related art.
Referring to FIG. 3, during the communication of the UE1 100 via the wireless communication network, if the P-GW 116 receives a UL IP packet 300 on an EPS bearer 118, the P-GW 116 may convert the source IP address of the UE1 100 into a public IP address of the UE1 100, in the UL IP packet 300, and transmit the modified IP packet 310 to the PDN 110. The modified IP packet 310 carrying the local IP address of the destination UE may not reach the destination UE as the local IP address of the destination UE is not a valid IP address in the PDN 110. The same problem may happen even for the IP packets transmitted by the destination UE to the UE1 100.
In one of the possible solutions when the path is switched from the direct communication path to the communication path via the wireless communication network, an application of the UE1 100 may establish a new IP connection to some servers of the PDN 110, and the UE1 100 may start communication with other UEs. However, such a solution does not provide seamless IP session continuity.
Alternatively, a new IP connection may be established between the UE1 100 and some servers of the PDN 110, and the new IP connection may tunnel the IP packets from the UE1 100 to another UE. A new IP connection may be established between another UE and the server of the PDN 110, and the new IP connection may tunnel the IP packets from another UE to the UE1 100. However, such a solution may require changes at the IP layer, and the IP layer needs to be aware of communication path switching. In addition, the IP layer may have more tunneling overhead.
Therefore, there is a need for a system and method for providing seamless IP session continuity when a communication path for a UE1 and another UE switches from the direct communication path to the communication path via the wireless communication network, or vice versa.
The above information is presented as background information only to assist with an understanding of the present disclosure. No determination has been made, and no assertion is made, as to whether any of the above might be applicable as prior art with regard to the present disclosure.